252Cf Fission Fragments Research Articles

Octupole deformation in 143,145,146Ba

Gamma rays emitted by fission fragments of 252Cf and measured using the Gammasphere array continue to give insight into neutron rich nuclei. Using our high statistics data, we have reexamined high-spin states and linking transitions associated with octupole correlations in 143,145,146Ba. This has been a region of interest, when it was proposed that near 145Ba there was a region of octupole deformation. In an even-A system, it is possible that rotational band structures are explainable by simplex quantum numbers, s=+1 and s=−1. The previous bands including octupole bands in 143,145,146Ba have been extended. The new s=i octupole bands in 145Ba and new s=−1 octupole bands in 146Ba have been identified. In addition, collective model analysis of energy displacement, rotational frequency and B(E1)/B(E2) ratios have been carried out. Evidence of the rotational consequences of octupole deformation in even-even and even-odd isotopes is given. These nuclei have trends as rotation stabilizes the vibrational degrees of freedom. The experimental results are in agreement with theoretical calculations using the interacting boson and boson-fermion models that are based on a universal nuclear energy density functional.

Secondary ion emission from C2H6:H2O ice by fission fragments

Water (H2O) ice is a common constituent of several astrophysical object surfaces; other condensed gases (e.g., CH4, CO2, NH3, and C2H6) also occur in specific bodies. Bombarded by cosmic rays, these molecules react among them, generating new molecular species, which are partially ejected to the gas phase via a process called sputtering. In the current work, C2H6:H2O ice is irradiated at an averaged temperature of 100 K by energetic multicharged ions (252Cf fission fragments of ∼ 65 MeV). The sputtered positive and negative secondary ions are detected and analyzed by time-of-flight mass spectrometry (PDMS-TOF). The projectile-surface collision induces the formation of ionic cluster series (H2O)nX (X = H2O+, H3O+, O− and OH−), and their yield distribution can be represented by the sum of two decreasing exponentials, suggesting the presence of a two distinct formation processes, one for the low cluster masses and another for the larger ones.

Influence of pre-exposure thermal annealing on etch rates of CR-39 nuclear track detectors: New findings

The influence of pre-exposure thermal annealing on CR-39 etch rates has been studied here thoroughly. Annealing experiments were conducted on CR-39 detectors prior to their exposure to 252Cf fission fragment source. The bulk etch rates were measured by using the weight loss method (WLM) and the fission track diameter method (FTDM). We report here a new quantitative result that the bulk etch rate decreases from the original surface of each CR-39 detector initially rapidly and then more slowly along the depth mimicking the exponential trend. These quantitative results are more pronounced for cases of higher annealing temperatures and larger annealing time intervals. This exponential drop of the bulk etch rate suggests that the interior of the CR-39 detector material is almost out of pre-exposure annealing. Our results reveal that the etch rates and the registration properties of the heavy ions are considerably altered in the near-surface layer of the annealed PADC.

Speeding up liquid-phase heavy element chemistry: Development of a vacuum to liquid transfer chamber (VLTC)

We present a new system, which is suitable for performing fast liquid phase chemistry experiments and gives access to shorter-lived isotopes of super heavy elements (SHE) than accessible with current techniques. With this novel vacuum to liquid transfer chamber (VLTC), which is mounted behind a physical preseparator, the desired isotopes are transported from the low-pressure side of the recoil separator directly into the liquid phase of a chemical experiment. Simulations on the kinematics of evaporation residues were performed using SRIM, validating the general plausibility of the VLTC concept. Subsequently, the feasibility was demonstrated with 250,252Cf fission fragments, which were collected in dilute nitric acid, separated on an ion exchange column and measured by γ-ray spectroscopy. Finally, tests on the mechanical and chemical stability of the system as well as measurements of the residence time in the liquid phase were performed.

ZOOHYGIENIC CHARACTERISTICS OF BIOTECHNOLOGICAL METHODS OF METABOLISM REGULATING OF CHICKENS EMBRYO IN THE PROCESS OF INCUBATION


 The research presents the results of experimental studies of the influence of various physicochemical factors (phonophoresis, electrophoresis, electrospray, diffusion, etc.) on the rate of transport of biologically active substances through the protective layer of hatching eggs shell of crossbred Haysex Brown. The aim of the study was to compare the effectiveness of the use of physicochemical methods of transportation of biologically active substances through the shell of hatching eggs of chickens. For the experiment, three batches of eggs were formed, which were obtained from layer hens Haysex Brown, 144 pieces in each experimental group. The kinetic parameters of BAS transport through bioceramic protective barriers of eggs were calculated based on the determination of BAS concentration on the surface and inside the egg by mass spectrometric method (mass spectrometer with ionization of 252Cf fission fragments "MSBH", (Ltd "SELMI", Sumy, Ukraine). The degree of permeability of bioceramic layers of the shell relative to the model gas mixture which is identical to the atmospheric air was studied by the method of V. Breslavets et other and the mass spectrometric method (gas mass spectrometer "MX 7304A"). Electron microscopic studies were performed on a scanning electron microscope REMMA-102; Visilog 6.11 (Noesis, Belgium) was used to process the obtained digital images to determine the number of shell microdefects per unit area of the digital image. It has been experimentally proved that to increase the efficiency of transport of biologically active substances (BAS) through the bioceramic layers of the shell of hatching eggs of Loman Brown hens, it is advisable to use ultrasonic treatment (phonophoresis, sonophoresis), substances - enhancers, including plant terpenes (L-menthol), DMSO and cyclodextrin. Phonophoretic treatment of hatching eggs increases the hatchability of eggs by 7.6%. At the same time, the gas permeability of the bioceramic layer increases significantly (by 0.43. 10-4 m3 / m2 s).

ZOOHYGIENIC CHARACTERISTICS OF BIOTECHNOLOGICAL METHODS OF METABOLISM REGULATING OF CHICKENS EMBRYO IN THE PROCESS OF INCUBATION

The research presents the results of experimental studies of the influence of various physicochemical factors (phonophoresis, electrophoresis, electrospray, diffusion, etc.) on the rate of transport of biologically active substances through the protective layer of hatchig eggs shell of crossbred Haysex Brown. The aim of the study was to compare the effectiveness of the use of physicochemical methods of transportation of biologically active substances through the shell of hatching eggs of chickens. For the experiment, three batches of eggs were formed, which were obtained from layer hens Haysex Brown, 144 pieces in each experimental group. The kinetic parameters of BAS transport through bioceramic protective barriers of eggs were calculated based on the determination of BAS concentration on the surface and inside the egg by mass spectrometric method (mass spectrometer with ionization of 252Cf fission fragments "MSBH", (Ltd "SELMI", Sumy, Ukraine). The degree of permeability of bioceramic layers of the shell relative to the model gas mixture which is identical to the atmospheric air was studied by the method of V. Breslavets et other and the mass spectrometric method (gas mass spectrometer "MX 7304A"). Electron microscopic studies were performed on a scanning electron microscope REMMA-102; Visilog 6.11 (Noesis, Belgium) was used to process the obtained digital images to determine the number of shell microdefects per unit area of the digital image. It has been experimentally proved that to increase the efficiency of transport of biologically active substances (BAS) through the bioceramic layers of the shell of hatching eggs of Loman Brown hens, it is advisable to use ultrasonic treatment (phonophoresis, sonophoresis), substances - enhancers, including plant terpenes (L-menthol), DMSO and cyclodextrin. Phonophoretic treatment of hatching eggs increases the hatchability of eggs by 7.6%. At the same time, the gas permeability of the bioceramic layer increases significantly (by 0.43. 10-4 m3 / m2 s).

Low-temperature chemistry induced by cosmic rays: positive and negative ion desorption from nitrile-bearing astrophysical ice analogues

ABSTRACT In cold core of dark molecular clouds, where the UV radiation from external sources is strongly attenuated, cosmic rays can induce chemical reactions on the surface of ice-covered grains promoting the ejection of the processed material to the gas phase. We report the positive and negative secondary ion emission from pure CH3CN, C2H3CN, and i-C3H7CN ices due to the bombardment of heavy ions (252Cf fission fragments), simulating the incidence of cosmic rays on to icy surfaces. The secondary ions emitted from each sample were analysed by time-of-flight mass spectrometry, using Plasma Desorption Mass Spectrometry technique. Several ionic species were identified, indicating strong fragmentation on the frozen surface. Proton-transfer processes are suggested to play a role for positive ion desorption, as evidenced by the protonated RCNH+ parent molecules and (RCN)nH+ ionic clusters. The high electron affinity of the cyano radical seems to contribute to the strong emission of CN−, as well as anions attributed to the CHmCN− fragment and (RCN)nCN− cluster series. Sputtering and desorption of ion clusters (positive and negative) induced by heavy ion bombardment are suggested to constitute a route by which new neutral or ionized molecular species may be delivered to the gas phase where thermal desorption is negligible.

Annealing of fission fragment tracks in CR-39 nuclear track detector — Phenomenological model

Abstract In this short paper, a new model for annealing of latent nuclear tracks is developed. Physical phenomenological picture or foundation of the model is presented using experimental spectra of 252Cf fission fragment tracks annealed at 75–175 °C for 5–30 min. Here, annealing of nuclear tracks refers to the reduction of track lengths during annealing or thermal treatment. A new annealing parameter (t/T2) is identified in the model, which is useful in understanding and analysis of annealing of nuclear tracks. In definition of the annealing parameter above, the quantities t and T are annealing time and temperature, respectively. The model allows deduction of the activation energy of annealing simultaneously from track annealing data, collected over all the annealing conditions (t, T). This model provides a quick methodology to study kinetics of nuclear track annealing. The presented model is validated using the experimental results of annealing of fission tracks in CR-39 detector. The determined value of activation energy of annealing is 0.204 ± 0.012 eV. Presented results and discussion can be extended to swift heavy ion (SHI) tracks.

CR-39 nuclear track detector: An experimental guide

The influence of preservation period of CR-39 detectors, in refrigerator and in the laboratory atmosphere, on bulk etch rate is studied. The effect of etching solution usage time on the bulk etch rate is also investigated. Analyses and quantitative results in the said cases are presented. Finally, precision results on the use of CR-39 as a charged particle detector are presented in a systematic manner. These results are selected from our radiation detection and measurement experiments, ranged over last two decades. Selected results (unpublished and published) include CR-39 measurements of 5.9 MeV antiprotons, 6.12 MeV alpha particles and spontaneous fission fragments of 252Cf. Our published results, presented here, are further analyzed and presented in comparison with new results and discussion. Experimental procedures of exposures, chemical etching, track measurements using the optical microscopy are described, keeping in view the new users and research students. Computer codes TRACK_Vision and SRIM were employed to provide a comparison with measurements of track parameters, where possible.

Radioluminescence of solid neodymium-doped laser materials excited by α-particles and fission fragments

The characteristics of radioluminescence of Nd3+ : Y3Al5O12 crystals and laser glasses under excitation by plutonium-239 (239Pu) α-particles, as well as by α-particles and spontaneous fission fragments of californium-252 (252Cf), are studied. The radioluminescence branching ratios βij for the transition from the 2F25/2 level to the 2S+1LJ levels in Nd3+ : Y3Al5O12 crystals are measured. Radioluminescence from the 2P3/2 level to low-lying levels is observed. The βij ratios for transitions from the high-lying 2F25/2, 4D3/2, and 2P3/2 levels are theoretically calculated. The lifetimes of metastable levels of Nd3+ excited by 252Cf fission fragments are measured. The efficiency of the conversion of energy of α-particlesand fission fragments to the energy of optical radiation of Nd3+ : Y3Al5O12 crystals and laser glasses is determined.

Secondary ion emission dynamics of solid ammonia bombarded by heavy ions

Relevant phenomena occurring in the projectile-solid interaction and the subsequent emission of secondary ions from the sample surface will be theoretically treated in this work. The goal is to determine the velocity and energy distributions of the secondary ions emitted from a target of solid ammonia, through the description of secondary electron emission by the nuclear track and the establishment of secondary ion trajectories. Calculations were made with the computer code SEID. Theoretical distributions, valid for secondary ions that no longer interact with the solid, were compared with the experimental distributions obtained for ammonia ice bombarded by 252Cf fission fragments. It was observed that ionic species of mass ~86 u, located within 10 A from the projectile impact point, are desorbed without being neutralized, unlike lighter ions (~18 u) that leave the surface from more distant regions. Considering the ionization energy (I = 35 eV) of NH4, the experimental value of 6 km/s was reproduced. These comparisons also show that the model partially describes the behavior observed in the energy distribution of the emitted ions. As a result, new processes are proposed to be included in the model.

Characteristics of a new plastic track detector of the CZ type

The registration parameters of a new plastic track detector (PTD) for nuclear particles have been experimentally investigated. The PTD is a modification of a CR-39 detector and is labeled CZ. As compared to the CR-39 detector with a similar chemical composition, the CZ PTD produced by the Semenov Institute of Chemical Physics from allyl diglycol carbonate (C12H18O7) has a considerably higher sensitivity and better dynamical (the track etching rate and the rate of etch removal of a substance from the surface of a PTD plate) and geometrical (etchable track length and diameter) registration parameters. Based on results of the calibration experiments with α particles of different energies, fission fragments of 252Cf, and accelerated 20Ne ions, the theoretical estimate was obtained for the threshold value of the specific ionization losses, the sensitivity, and the detection efficiency for nuclear particles, beginning with protons.

Cluster ion emission from LiF induced by MeV Nq+ projectiles and 252Cf fission fragments

Ion cluster desorption yields from LiF were measured at PUC-Rio with ≈0.1 MeV/u Nq+ (q = 2,4,5,6) ion beams by means of a time-of-fight (TOF) mass spectrometer. A 252Cf source mounted in the irradiation chamber allows immediate comparison of cluster emissions induced by ≈65 MeV fission fragments (FF). Emission of (LiF)nLi+ clusters are observed for both the N beams and the 252Cf fission fragments. The observed cluster size n varies from 1 to 6 for Nq+ projectiles and from 1 to ≈40 for the 252Cf-FF. The size dependence of the Y(n) distributions suggests two cluster formation regimes: (i) recombination process in the outgoing gas phase after impact and (ii) emission of pre-formed clusters from the periphery of the impact site. The corresponding distribution of ejected negative cluster ions (LiF)nF− closely resembles that of the positive secondary (LiF)nLi+ ions. The desorption yields of positive ions scale as Y(n) ∼ q5. A calculation with the CASP code shows that this corresponds to a cubic scaling ∼Se3 with the electronic stopping power Se, as predicted by collective shock wave models for sputtering and models involving multiple excitons (Frenkel pair sputtering). We discuss possible interpretations of the functional dependence of the evolution of the cluster emission yield Y(n) with cluster size n, fitted by a number of statistical distributions.

Expansion of the radioactive ion beam program at Argonne

The Argonne Tandem Linear Accelerator System (ATLAS) at Argonne National Laboratory (ANL) provides a wide range of stable ion beams and radioactive beams which have contributed to our understanding of nuclear structure and reactions. Until now, most radioactive ion beams at ATLAS were produced in flight using light-ion reactions such as (p, n), (d, n), (d, p), (d,3He), and (3He,n). Within the next few months, the radioactive ion beam program at ATLAS will acquire much extended, new capabilities with the commissioning of a new facility: the CAlifornium Rare Isotope Breeder Upgrade (CARIBU). CARIBU will supply ion beams of 252Cf fission fragments, which are thermalized in a gas catcher. The singly- and doubly-charged ions extracted from the gas catcher will be mass-separated and either delivered to a low-energy experimental area, or charge bred with a modified ECR source and subsequently reaccelerated by the ATLAS facility. Properties of hundreds of these neutron-rich nuclides will be investigated using ion traps, decay stations, the newly commissioned HELical Orbit Spectrometer (HELIOS), and other available experimental equipment such as Gammasphere and the FMA. HELIOS was constructed to take advantage of rare ion beams, such as those provided by CARIBU, through light-ion transfer reactions in inverse kinematics, and represents a new approach to the study of direct reactions in inverse kinematics which avoids kinematic broadening. Experiments are currently being conducted with HELIOS, and first results with the d(28Si,p) and d(12B,p) reactions have shown excellent energy resolution.

Theoretical Investigation on the Stability of Negatively Charged Formic Acid Clusters

Recent experimental results on negatively charged formic acid clusters generated by the impact of (252)Cf fission fragments on icy formic acid target are compared to quantum mechanical calculations. Structures for the clusters series, (HCOOH)nOH(-), where 2 < or = n < or = 4, are proposed based on ab initio electronic structure methods. The results show that cluster growth does not have a regular pattern of nucleation. A stability analysis was performed considering the commonly defined stability function. Temporal behavior of the clusters was evaluated by Born-Oppenheimer molecular dynamics to check the mechanism that provides cluster stability. The evaluated temporal profiles indicate the importance of hydrogen atom migration between the formic acid moieties in maintaining the stability of the structures and the water formation due to hydrogen abstraction by the hydroxyl approach.

THE HELIOS SPECTROMETER AND THE RADIOACTIVE BEAM PROGRAM AT ARGONNE

The near-term radioactive beam capabilities of ATLAS include radioactive beams produced in flight in a gas cell, or starting in the fall of 2009, re-accelerated beams of 252 Cf fission fragments provided by the new CARIBU injector. The availability of such exotic beams will allow for detailed studies of the single-particle aspects of nuclear structure in neutron-rich nuclei reaching out to the astrophysical r-process path by employing light-ion reactions in inverse kinematics. The HELIOS spectrometer is based on a new concept that is especially well suited for such studies. This concept was recently demonstrated using the reactions D (28 Si , p )29 Si with a (stable) 168 MeV 28 Si beam. Since then D (12 B , p )13 B , D (17 O , p )18 O , and D (15 C , p )16 C have been studied successfully. The combination of neutron-rich beams from CARIBU and the HELIOS spectrometer opens a fertile research area of precision studies of the single particle strengths and collective excitations in exotic nuclei, and is likely to have applications in other reactions as well.

Stopping power of fission fragments of 252Cf in argon: A comparison between experiments and simulation with the SRIM code

The stopping power of ions in gases can be computed by codes, such as SRIM, based on experimental data and theories. However, no available code has been tailored to deal with the specific properties of fission fragments when interacting with gas. This is, however, of key interest for fission chambers, in which the electric signal results from the ionisation of a gas by fission fragments. We compared experimental data available in the literature with those computed with SRIM. In spite of a underestimation of the energy loss per unit length, SRIM gives qualitatively good results, thus is an useful tool to study the stopping power of fission fragments in gases. However, getting more comprehensive experimental data should be beneficial.

Nuclear track detection using thermoset polycarbonates derived from pentaerythritol

The paper describes the synthesis and performance of two polymers as nuclear track detectors, both having alpha sensitivity higher than that of the widely-used polymer CR-39. A homopolymer (PPETAC) from pentaerythritol tetrakis(allyl carbonate) (PETAC) monomer and its various copolymers with allyl diglycol carbonate (ADC) prepared by cast polymerization were successfully used as nuclear track detectors. The copolymer PETAC:ADC 4:6 weight percent shows maximum alpha sensitivity, almost double that of CR-39 under identical experimental conditions. This copolymer can reveal alpha particle tracks from 239Pu source in about 60 min and 252Cf fission fragment tracks by chemical etching in less than 30 min, compared to about 120 min and 45 min respectively, required by CR-39. The polymers can be conveniently etched using aqueous sodium hydroxide.

Theoretical and Experimental Study of Negative LiF Clusters Produced by Fast Ion Impact on a Polycrystalline 7LiF Target

The emission of negative cluster ions produced by the impact of approximately 60 MeV (252)Cf fission fragments on a (7)LiF polycrystalline target is analyzed. The negative ion mass spectrum is dominated by the ((7)LiF)(n)F(-) series, n = 1 to approximately 30. The desorption yield distribution of the ((7)LiF)(n)F(-) members has a maximum at n = 2 and then decreases as the sum of two exponentials whose decay parameters are k(Fast) = 0.9 and k(Slow) = 0.08. These k values are the same as those observed for the positive series and close to others obtained for condensed gas targets. Relative cluster ion stabilities, deduced from the experimental ion abundances for the (LiF)(n)F(-) series, are proposed to be correlated with theoretical structures according to their internal energy by using the deviation plot (D-plot) methodology. A pool of candidate cluster structures was generated using a genetic algorithm and further analyzed and optimized using density functional theory (DFT) with the hybrid functional B3LYP (DFT/B3LYP) and Moller-Plesset perturbation theory (MP2). For the small clusters (n = 1 to 2), the most stable structures are found to be linear, whereas the larger clusters (n = 4 to 6) present cubic or polyhedral structures. Fragmentation energies, ionization potentials, and relative stabilities are reported for the most abundant families of the (LiF)(n)F(-) and (LiF)(n)(-) series.

Equivalent properties of single event burnout induced by different sources

The experimental results of single event burnout induced by heavy ions and 252Cf fission fragments in power MOSFET devices have been investigated. It is concluded that the characteristics of single event burnout induced by 252Cf fission fragments is consistent to that in heavy ions. The power MOSFET in the “turn-off" state is more susceptible to single event burnout than it is in the “turn-on" state. The thresholds of the drain-source voltage for single event burnout induced by 173 MeV bromine ions and 252Cf fission fragments are close to each other, and the burnout cross section is sensitive to variation of the drain-source voltage above the threshold of single event burnout. In addition, the current waveforms of single event burnouts induced by different sources are similar. Different power MOSFET devices may have different probabilities for the occurrence of single event burnout.